JPS6151461B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a control device for an electrostatic recording device, and more particularly, the present invention relates to a control device for an electrostatic recording device, and more specifically, a control device for controlling a photoreceptor including a photoconductor layer using a laser beam, an optical fiber tube (OFT), or the like. The present invention relates to a control device for an electrostatic recording device of a type that forms an electrostatic latent image on a photoreceptor by performing the following steps.

BACKGROUND OF THE INVENTION In recent years, systems that utilize an electrophotographic image creation process have been proposed or provided as printers that receive and record electrical signals such as computer output or facsimile transmission signals. In this type of printing system, in order to convert electrical signals into optical signals and project them onto the photoreceptor, an OFT (optical fiber tube) or a laser beam is used to direct the photoreceptor in the direction of the photoreceptor's movement. A slice scan is performed in a direction (main scanning direction) substantially perpendicular to the main scanning direction (sub-scanning direction), and an output pattern such as a character is formed by appropriately controlling the switching of the optical signal. This type of printer has various advantages as a non-impact printer, but since it uses an electrophotographic image forming mechanism and process such as a surface and a photoreceptor, it is less effective than a conventional impact printer. However, this method has disadvantages in that it requires control for stabilizing the output image and a control mechanism associated therewith.

Purpose The present invention aims to provide a control device for efficiently performing image stabilization control in such a printer, and furthermore, it is an object of the present invention to provide a control device for efficiently performing image stabilization control in such a printer, and further for effectively controlling image exposure performed by line scan. The object of the present invention is to provide a control device that can be used to detect the electrical charge level of a photoreceptor and the potential after exposure, and thereby perform control for stabilizing an image. .

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an electrostatic recording device of the type that performs line scanning using a laser beam, and first, the configuration of the recording device and the outline of the printing operation will be explained using this diagram.

A photoreceptor drum 101 is supported in the printing mechanism section 1 so as to be rotatable clockwise in the figure, and around it are a charging charger 102, a surface electrometer S, a developing device 103, a sub-eraser 104, and a transfer charger 105. , subcharger 106, cleaning blade 107 and eraser lamp 10
8 etc. are arranged in sequence, and the photosensitive drum 101
As it rotates, its surface is uniformly charged by the charging charger 106, and is irradiated with laser light from the laser beam irradiation mechanism section 2, which will be described later, to form an image pattern such as a character. The developing device 103 to which a polar bias voltage V _B is applied performs reversal development in which toner (not shown) charged with the same polarity as the charged charge is attached to the beam projection section, and this toner image is transferred to the charged charge. A visible image is formed on the recording paper P by transferring it onto the recording paper P by a transfer charger 105 having a polarity opposite to that of the material.

The recording paper P after the transfer is sent to a fixing device section (not shown), where the toner image is fixed and the printing operation is completed. On the other hand, the photosensitive drum 101 after the transfer is transferred to the photosensitive drum 101 at the transfer charger 105.
Since the entire width of the recording paper P is charged with the opposite polarity to the charged surface, the potential after the opposite charging is different between the width part of the recording paper P and the other parts, which may cause negative effects in the subsequent cleaning and optical erase process. In order to prevent this, the surface potential of the drum 101 is once made to the same polarity as the toner by a subcharger 106, and then the residual toner and charge are removed by a cleaning blade 107 and an erase lamp 108, and the toner is returned to the charging process. It is.

The relationship among the charging potential Vo, the exposure potential Vi, the developing bias potential _VB, etc. will be explained with reference to FIG. In this embodiment, the charged potential Vo is assumed to be of positive polarity.

The surface of the photosensitive drum 101 is charged to a potential Vo by the charging charger 102, and when the laser beam is irradiated, the potential drops to Vi. In this state, since the developing toner is positively charged, the developing bias VB is Vi<V _B
<Set the potential according to the relationship of Vo.

At this time, the voltage V _B −Vi is related to the image density,
The voltage Vo- _VB is related to image fog. The characteristics of the photoreceptor change due to temperature changes and fatigue due to continuous use, and the initial charge level changes accordingly.
Since Vo and the potential Vi of the exposed area vary, if the voltage of the charging charger 102 and the developing bias V _B are constant, toner adhesion (fogging) to the non-image area may cause a change in image density. in particular,
Using a selenium Se-based photoconductive material as a photoreceptor,
Vo = 300 [V], V _B = 200 [V] and Vi50
When set to [V], if Vo-V _B becomes 70 [V] or less due to a decrease in the charging potential Vo, fogging will occur, and conversely, if Vo increases to Vo450 [V], the amount of water in the developer will increase. Inconveniences such as carrier adhesion may occur. Furthermore, if the exposure potential Vi increases and V _B -Vi decreases, good image density will not be obtained.

Therefore, in the present invention, the above-mentioned
Vo or Vi is measured, and based on this, the charging voltage of the charging charger 102, the developing bias _VB , the light amount of the laser beam, etc. to be described later are controlled,
This solves the above-mentioned inconvenience.

FIG. 3 is a plan view showing a schematic configuration of the laser beam irradiation mechanism section 2. As shown in FIG.

The laser beam LB from the laser 201 is narrowed down in beam diameter by the lens _L1 , and then passed through the prism.
The primary light enters the acousto-optic modulation AO element 202 via P ₁ and P ₂ and is diffracted here. The beam diameter is returned to the original by lens L ₂ , and the beam diameter is further expanded by lenses L ₃ and L ₄ . is incident on a polygon mirror (for example, a decahedron) that rotates at high speed, and a line scan is performed using the deflection angle accompanying the rotation of each surface of the polygon mirror 203. At this time, the laser beam LB is corrected for its inclination angle (scan deflection on the photoconductor drum surface) by the cylindrical lens Sv and the toroidal lens 204, and is returned to parallel light.
and is projected onto the photosensitive drum 101 via the reflecting mirror _M2 . The lens system 205 maintains a constant scanning speed on the focal plane when the deflection angular velocity of the beam LB is constant, and the relationship between the image height y and the deflection angle θ is expressed as y=f・
This is to replace θ.

In the above configuration, the laser beam LB is A.
The photosensitive drum 1 is modulated by the O element 202.
Switching is controlled in an appropriate synchronous relationship with the rotational speed of 01, and patterns such as characters are formed on the photosensitive drum 101. The AO element 202 performs a switching operation by bending the optical path of the laser beam LB using regular unevenness in density in a material formed by the propagation of ultrasonic waves through the material, that is, a spatial phase grating. However, by controlling the gain of the AO element 202 using the AO driver 206, the amount of light of the beam LB reaching the photoreceptor 101 can be controlled. Therefore, it is possible to correct the above-mentioned fluctuation in the exposed portion potential Vi by adjusting the light amount of the laser beam LB.

In FIG. 3, d ₁ indicates the width of the effective development area from the center of the axial length of the photosensitive drum 101, and d ₂
Similarly, d3 indicates the maximum width of the recording paper P, and _d3 similarly indicates the width of the effective charging area of the charging charger 102 and the maximum scanning width by the laser beam LB. The surface electrometer S has the widths d ₃ and d ₂ as shown in the figure.
It is preferable to position it between. That is, by arranging it at this position, the above-mentioned potentials Vo and Vi can be detected and the charging charger 102 and the AO driver 206 can be controlled, if necessary, even during printing operation.

FIG. 4 is a circuit diagram showing an example of the control device of the present invention.

The output of the surface electrometer S is sent to the comparator CO via the amplifier AM and switch SW1 for switching Vo and Vi detection.
1.Input to CO2. Comparator CO1 is charged
This is for Vo control, and the reference voltage Vso and detection potential Vo
This is an analog comparator that compares the two and changes the output state according to the difference. Similarly, the comparator CO2 is used to control the exposure section potential Vi, and compares the reference voltage Vsi and the detected potential Vi.

As a control operation, first, the photosensitive drum 10 is turned on by turning on the start switch SW2 of the printing mechanism section 1 or by a start signal from a computer.
1 starts rotating and the charging, erasing, etc. devices are activated, the control circuit 301 is activated, and the selector switch SW1 is first set to the comparator CO1 side.
At this time, the laser beam LB remains stopped,
Alternatively, if an image is being formed, switching is controlled by the AO element 202 so as to scan up to the width d ₁ or d ₂ , so that the surface of the photoreceptor facing the surface electrometer S is not exposed to light. .
Therefore, the initial charging potential Vo is detected by the electrometer S, which is compared with the reference voltage Vso by the comparator CO1, and the difference output is used to control the charging charger 102.
The driver 302 of the high voltage power supply 303 is controlled until Vo=Vso. Vo=Vso and the output of the comparator CO1 becomes "0", and when this is input to the control circuit 301, the laser beam LB
A full scan of the width d ₃ or a scan of only the width d ₃ −d ₂ is performed depending on the width. After a slight delay while the scanned and exposed photoreceptor portion rotates to the electrometer S, the changeover switch is turned on.
Switch SW1 to the comparator CO2 side. At this time, since the surface electrometer S detects the potential Vi after being exposed to the beam, this is detected by the comparator CO2.
compares it with the reference voltage Vsi, and controls the driver 206 of the AO element 202 by the difference output,
Continue this until Vi=Vsi. And Vi
When Vsi is reached, the Vo detection operation is performed again, or the detection operation is stopped for a predetermined period of time.

Incidentally, such detection and control operations can be performed even during normal printing operations if the surface electrometer S is positioned between the widths d ₃ and d ₂ as described above. This may be done in advance by setting an appropriate control mode before starting the printing operation, or the control mode may be automatically executed with the start of the printing operation. In addition, if you set a timer in advance and control the developing bias V _B in accordance with the output of the comparator when performing such control operations during printing, good image density can always be obtained and fog can be prevented. can also be prevented.

FIG. 5 shows a schematic circuit configuration when the above-described control is performed using a microcomputer MC, and FIG. 6 shows an example of the operating procedure in a flowchart.

In Figure 5, the output of electrometer S is output from amplifier AM
to A-D (analog-digital) converter 401
Microcomputer MC input port through
Input to PAo. The input port _PA1 receives the ON signal of the start switch SW2 or the start signal from the computer. output port
PD ₁ , PD ₂ and PD ₃ output signals for controlling the charger's high-voltage power supply 303, the AO element 202, and the developing bias _VB, respectively.

The flowchart in FIG. 6 shows the control operation procedure within the microcomputer MC, and here an example is shown in which the printing operation and the control operation for controlling the surface potential, etc. are executed at different timings.

In the step, if the recording device is in operation, the plug is determined to be "1", and if the plug is "0", the step determines whether the start switch SW2 is on (start signal input), and when the start signal is output. In addition to setting the operation flag to "1", flags FA and FA related to control operations of Vo and Vi, which will be described later, are set.
Set FB to “0”.

In this step, when the start signal is issued, it is determined whether the operation mode of the recording device is selected as control mode or normal print operation mode, and if it is in control mode, the control flag is set to "1". , rotation of the photosensitive drum 101,
The operation of the charger 102 and the eraser 108 are started, and the timer TA is set.
If not in control mode, normal printing operation (first
(see figure and explanation of printing operation).

In the step, the control mode may be selected by the user by operating an appropriate switch, or the control mode may be automatically selected by turning on the power or by a signal such as a timer signal every predetermined time. . Note that when the control mode is automatically selected, the determination of the start signal of the step is replaced with the determination of the start signal of the control mode. In addition, the timer TA in the step includes the photoreceptor drum 101, charger 102, eraser 10,
This is a timer for setting a slight delay time from when the photoreceptor drum 101 etc. starts operating to when the surface potential control operation starts.
The period of time required for the portion irradiated with light by the eraser 108 to reach the surface electrometer S section as the photoreceptor 108 rotates, preferably with the sub-eraser 104, transfer charger 105, and sub-charger 106 also operating. The control operation is started after the drum 101 has rotated one revolution or more.

In the step, the control operation for the charged voltage level Vo is started, that is, the plug is determined to be set to "1" by the time-up of the timer TA in the step. When the flag FA is "1", the potential Vo detected by the surface electrometer S is compared with the reference voltage data Vso recorded in a memory (not shown), and if they are not equal, the control circuit 302 of the high voltage power supply is activated in a step. control and repeat this until they are equal.

When Vo=Vso, the flag FA is set to “0”.
At the same time as the Vo detection operation is finished, the laser beam LB is controlled to perform a full scan or to scan across the width d ₃ - d ₂ mentioned above, and the next control operation for the exposed part potential Vi is started, so a slight delay time is set. Set timer T-B. This timer T-
The setting time of B is similar to the above-mentioned timer T-A,
This is the time taken for the portion exposed by the laser beam LB to reach the S section of the electrometer.

In the step, a control operation for the exposed portion potential Vi is started, that is, a flag is determined which is set to "1" by the time-up of the timer T-B in the step. When the flag FB is "1", the potential Vi detected by the surface electrometer S is compared with the reference voltage data Vsi stored in a memory (not shown) in steps, and the voltage of the AO element 202 is increased in steps until they become equal. The driver 206 is controlled to adjust the light intensity of the laser beam LB.

When Vi=Vsi, flag FB is set to “0” and Vi
At the same time as the detection operation ends, the laser beam LB
OFF or the scanning of the above width d ₃ -d ₂ parts is completed, the charger is turned OFF, and the timer TC is set.

After the control operation is completed, the timer T-C erases the surface potential of the photoreceptor drum 101 and then resets the drum 1.
This is a timer for stopping 01 and preparing for printing operation.

Note that the steps collectively represent the control of the normal printing operation of the recording apparatus.

The flowchart explained above shows an example in which the voltage control operation and the print operation are executed at different timings, but as mentioned above, the potential control can also be executed during the print operation. In this case, since the drum, charger, eraser, etc. are all in operation, the rotation control of the drum 101 is performed from the processing procedure shown in FIG.
Charger, eraser ON/OFF control, etc. are omitted, and scanning of the laser beam LB to the width d ₃ −d ₂ part and detection and control of Vo and Vi may be related. When controlling the potential during the printing operation in this way, controlling the developing bias V _B can better prevent fog and stabilize the image density.

In addition, when controlling the exposed part potential Vi, the light amount of the laser beam LB is adjusted by controlling the gain of the AO element 202 in the above embodiment, but this is because the light intensity of the laser beam LB is adjusted in the optical path of the beam.
This may be achieved by providing an element capable of controlling light transmittance such as EC (electrochromic).

Effects As explained below, in the present invention, a photoreceptor moving in the sub-scanning direction is charged by a charging means, and a line scan is performed in the main-scanning direction using a switching-controlled optical signal at an exposure position to generate an electrostatic charge on the photoreceptor. a potential detection means, which is provided downstream of the exposure position in an electrostatic recording device that forms a latent image, and detects the surface potential of the photoreceptor charged by the charging means when it is not exposed to the optical signal and after being exposed to the light signal; Controlling the charging means to correct the surface potential detected by the potential detection means during exposure to a first predetermined potential, and correcting the surface potential detected by the potential detection means during exposure to a second predetermined potential. Since the control device is characterized in that it is equipped with a control means for controlling the exposure amount, the surface potential of the photoreceptor can be adjusted by effectively utilizing the fact that image exposure is performed by line scan of a laser beam or the like. etc., and can efficiently stabilize image density and prevent fogging.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a schematic configuration of an electrostatic recording device, Fig. 2 is a diagram for explaining transfer and development, Fig. 3 is a diagram showing a schematic configuration of a laser optical mechanism, and Fig. 4 is a diagram showing a control of the present invention. FIG. 5 is a block diagram showing a specific example of the apparatus, also using a microcomputer, and FIG. 6 is a flowchart showing its processing procedure. 1... Printing mechanism section, 2... Laser beam irradiation mechanism section, 101... Photosensitive drum, 102...
Charging charger, 103...Developing device, 104
... Sub-eraser, 105 ... Transfer charger, 106 ... Sub-charger, 108 ... Eraser, 201 ... Laser, 202 ... AO (acousto-optic modulation) element, 203 ... Polygon mirror, 2
06...AO driver, 301...Control circuit, 3
03...High voltage power supply, S...Surface electrometer, SW1...
...Selector switch, SW2...Start switch,
MC...Microcomputer, Vo...Charging potential, Vi...Exposure potential, _VB ...Development bias,
Vso, Vsi...Reference voltage (voltage data), CO1,
CO2...Analog comparator.

Claims (1)

[Claims] 1. In an electrostatic recording device in which a photoreceptor moving in the sub-scanning direction is charged by a charging means, and an electrostatic latent image is formed on the photoreceptor by line-scanning in the main-scanning direction using a switching-controlled optical signal at an exposure position. potential detecting means, which is provided downstream of the exposure position and detects the surface potential of the photoreceptor charged by the charging means when not exposed to the optical signal and after being exposed;
Controlling the charging means to correct the surface potential detected by the potential detection means during unexposed to a first predetermined potential, and correct the surface potential detected by the potential detection means during exposure to a second predetermined potential. 1. A control device for an electrostatic recording device, comprising: control means for controlling an exposure amount so that the amount of exposure is controlled.